Plasma display device, luminescent device and image and information display system using the same

ABSTRACT

The present invention provides a plasma display device, a luminescent device, and an image display system each having an excellent moving-image quality, a long lifetime, and high performance. The plasma display device has a plasma display panel having at least a pair of substrates, a discharge gas space formed between the pair of substrates, electrodes formed on the respective opposing surfaces of the substrates, and a phosphor layer formed on the surface of one of the pair of substrates in contact with the discharge gas space and a driver circuit for driving the panel via the electrodes. In the plasma display device, the decay time ({fraction (1/10)} decay time) of light generated from each of the phosphor layers for providing red, green, and blue emission which compose the phosphor layer is not more than 8 ms. The plasma display device and the luminescent device use a blue phosphor (a divalent europium activated alkali earth silicate phosphor) having high performance under excitation caused by a vacuum UV beam and a low-speed electron beam and a composition represented by the following compositional formula:  
     (Ae) a-c (Ae′) b Si x O y :Eu c .

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a plasma display device used ina broadcast receiver or for image display, to a luminescent deviceexcited by a rare gas resonance UV beam or a low-speed electron beam,and to an image display system using the display device and theluminescent device.

[0002] In recent years, a plasma display device using a plasma displaypanel (hereinafter simply referred to as PDP) has been mass-produced asa flat-panel display device used in a broadcast receiver or a computerterminal or for image (video) display.

[0003] The plasma display device performs color display by causing aphosphor disposed in an extremely small discharge space containing arare gas in the PDP to emit light by using, as an excitation source, ashort-wavelength UV beam (which has a resonance line at 147 nm or 172 nmif xenon is used as the rare gas) generated in the negative glow regionof the discharge space.

[0004] In the PDP of the plasma display device, the resonance line of arare gas shorter in wavelength than the resonance line of mercury vapor,which is at 253.7 nm, or the like is used as an excitation source forthe phosphor. The short wavelength limit thereof is the wavelength ofthe resonance line of helium, which is 58. 4 nm.

[0005] An exemplary structure of the gas discharge cell is as shown in“Technology & Materials of Color Plasma Display Panel” published by CMCPublishing Co. Ltd. A representative structure thereof is shown in FIG.9. FIG. 9 is an exploded perspective view showing the structure of atypical surface-discharge color plasma display device (PDP). The PDPshown in FIG. 9 is a reflective PDP obtained by bonding a front glasssubstrate 10 and a rear glass substrate 20, each composed of a glasssubstrate, to each other in integral relation and forming phosphorlayers 24, 25, and 26 in red (R), green (G), and blue (B) colors,respectively, on the rear glass substrate 20.

[0006] A pair of sustaining discharge electrodes 11 and 12 are formed inparallel to have a specified distance therebetween on the surface of thefront glass substrate 10 opposing the rear glass substrate 20. The pairof sustaining discharge electrodes 11 and 12 are composed of transparentelectrodes. Opaque bus electrodes 13 and 14 for compensating for theconductivity of the transparent electrodes are provided in superimposingrelation on the sustaining discharge electrodes 11 and 12.

[0007] These electrodes 11 to 14 are covered with a dielectric (such aslead glass) layer 15 for AC driving. The dielectric layer 15 is providedwith a protection film 16 made of a magnesium oxide (MgO).

[0008] Magnesium oxide (MgO), which is high in resistivity forsputtering damage and in secondary electron yield, functions to protectthe dielectric layer 15 and lower a discharge initiation voltage.

[0009] The rear glass substrate 20 has, on the surface thereof opposingthe front glass substrate 10, a group of electrodes consisting ofaddress electrodes 21 which are orthogonal to the pair of sustainingdischarge electrodes 11 and 12 on the front glass substrate 10. Theaddress electrodes 21 are covered with a dielectric layer 22. Barrierribs 23 for separating the address electrodes 21 from each other areprovided on the dielectric layer 22 to prevent the expansion of adischarge (define a region for the discharge). The barrier ribs 23 arecomposed of a low-melting glass and formed with equal spacings to havethe same heights and identically configured sidewalls.

[0010] The phosphor layers 24, 25, and 26 are coated successively instripes in such a manner as to cover the groove surfaces between thebarrier ribs 23. The formation of the phosphor layers 24, 25, and 26 isperformed by coating, on the rear glass substrate 20 having the addresselectrodes 21, the dielectric layers 22, and the barrier ribs 23 formedthereon, phosphor pastes prepared by mixing phosphor particles formingthe phosphor layers 24, 25, and 26 and vehicles by a method such asscreen printing and then removing a volatile component therefrom bybaking.

[0011] A discharge gas (a gas mixture of, e.g., helium, neon, xenon, andthe like) is sealed in the discharge space between the front glasssubstrate 10 and the rear glass substrate 20, though it is not depictedin FIG. 9.

[0012] In the PDP, a discharge cell (a unit light-emitting region or adischarge spot) is selected by either one of the sustaining dischargeelectrodes 11 and 12, e.g., the sustaining discharge electrode 12 andthe address electrode 21 and a gas discharge is caused repeatedly in theselected discharge cell through a sustained discharge between thesustaining discharge electrodes 11 and 12.

[0013] A vacuum UV beam resulting from the gas discharge excites thephosphor layers in the region so that visible emission is obtained.Color display is obtained by combining emission of each of unit cellshaving the red, green, and blue phosphor layers 24, 25, and 26corresponding to the three primary colors.

[0014] Color PDPs which have been improved increasingly in performanceyear after year are replacing direct-view cathode ray tube colortelevisions. For the PDPs to be widespread as major large-scaletelevisions for home use as television broadcast receivers, they shouldhave a higher moving-picture quality and a longer lifetime.

SUMMARY OF THE INVENTION

[0015] It is therefore an object of the present invention to provide redand green phosphor layers capable of implementing a higher-performancePDP with an improved moving-picture quality and a longer lifetime.

[0016] These and other objects and novel features of the presentinvention will be apparent from the description and accompanyingdrawings of the present specification.

[0017] The moving-image quality of a plasma display device is affectedby the decay time of visible light from each of phosphors emitting lightin red, green, and blue colors. In the case where the driving frequencyof the display is 60 Hz, if the decay time becomes 16.6 ms or more, thetailing of emitted light is still observed in the subsequent cycle,resulting in disturbance in a display image. To prevent this, the decaytimes ({fraction (1/10)} decay time) of the phosphors should beminimized. In practical applications, however, a moving image can bedisplayed with a considerably high quality if the decay times arereduced to about 8 ms or less. If the decay times can further be reducedto 6 ms or less, a moving image can be displayed in most cases with ahigh quality. Various red phosphors and green phosphors were thereforeprototyped and the decay times of the phosphors in a PDP were evaluated.It is to be noted that the decay time of a blue phosphor used in acurrent PDP need not particularly be shortened since it is extremelyshort (1 ms or less).

[0018] As a result, it was found that a green phosphor was preferablycomposed of a Zn₂SiO₄:Mn phosphor having a Mn/Zn composition ratio of0.05 or more. It was also found that a green phosphor preferably had acomposition obtained by mixing the Zn₂SiO₄:Mn with one or more selectedfrom the group consisting of (Y,Gd,Sc)₂SiO₅:Tb, (Y,Gd)₃(Al,Ga)₅O₁₂:Tb,(Y,Gd)₃(Al,Ga)₅O₁₂:Ce, (Y,Gd)B₃O₆:Tb, and YBO₃:Tb phosphors.

[0019] On the other hand, it was found that a red phosphor preferablyhad a composition obtained by mixing (Y,Gd)BO₃:Eu with either one of(Y₂O₃):Eu and (Y,Gd) (P,V)O₄:Eu.

[0020] Although the present inventors developed previously a divalenteuropium-activated alkali earth silicate phosphor as a blue phosphor foran electron beam (Japanese Laid-Open Patent Publication Nos. SHO 64-6087and HEI 01-167394), the evaluation thereof with the use of a vacuum UVbeam and a low-speed electron beam has not been performed yet. Thepresent invention has been achieved by finding, for the phosphor inquestion, a composition having an excellent color tone and a highluminous efficiency under excitation caused by a vacuum UV beam and alow-speed electron beam. The phosphor according to the present inventionis represented by the following compositional formula:

(Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y):Eu_(c)

[0021] wherein Ae is at least one alkali earth element selected from Sr,Ca, and Ba; Ae′ is at least one element selected from the groupconsisting of Mg and Zn; a is 1, 2, or 3; b is 1 or 0; x is 1 or 2; andy is 4, 6, 7, or 8. One or more phosphor compositions selected fromthose represented by the foregoing compositional formula were found tobe suitable.

[0022] The foregoing object is attainable by applying the foregoing red,green, and blue phosphors to respective phosphor layers providing redand green emission in a PDP.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is an exploded perspective view showing a structure of aplasma display panel in a plasma display device according to EMBODIMENT1 of the present invention.

[0024]FIG. 2 is a cross-sectional view showing a structure correspondingto one pixel in the plasma display panel according to EMBODIMENT 1;

[0025]FIG. 3 is a cross-sectional view showing a structure correspondingto one pixel in a plasma display panel according to EMBODIMENT 2 of thepresent invention;

[0026]FIG. 4 is a view showing the spaces between barrier ribs whichcorrespond to one pixel in a plasma display panel according toEMBODIMENT 3 of the present invention;

[0027]FIG. 5 is a block diagram showing a schematic structure of aplasma display panel using the plasma display panel according to each ofthe foregoing embodiments;

[0028]FIG. 6 is a block diagram showing a schematic structure of anexample of a plasma display module comprising the plasma display panelshown in FIG. 5;

[0029]FIG. 7 is a block diagram showing a schematic structure of anexample of a plasma display monitor having the plasma display moduleshown in FIG. 6;

[0030]FIG. 8 is a block diagram showing a schematic structure of anexample of a plasma display television system having the plasma displaymodule shown in FIG. 6; and

[0031]FIG. 9 is an exploded perspective view showing a structure of aplasma display panel in a typical surface-discharge color plasma displaydevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Referring now to the drawings, the embodiments of the presentinvention will be described in detail.

[0033] Embodiment 1

[0034]FIG. 1 is an exploded perspective view showing a structure of aPDP in a plasma display device according to EMBODIMENT 1 of the presentinvention.

[0035]FIG. 2 is a cross-sectional view showing a structure correspondingto one pixel in the PDP according to the present embodiment. Detaileddescription of the PDP of the plasma display device according to thepresent embodiment will be omitted since the structure thereof issubstantially the same as that of the aforementioned PDP shown in FIG. 9except that a phosphor layer 24 is filled with a red phosphor preparedby mixing a (Y, Gd)BO₃:Eu phosphor material with a Y₂O₃:Eu phosphor,which is a characteristic of the present invention. The phosphor layer25 is filled with a green phosphor which is a Zn₂SiO₄:Eu phosphor usedconventionally and exhibiting a {fraction (1/10)} decay characteristicof 6 ms. FIG. 2 shows the front glass substrate 10 of the PDP that hasbeen rotated by ±90°.

[0036] In a PDP such as the surface-discharge color PDP according to thepresent embodiment, a discharge is induced by, e.g., applying a negativevoltage to a sustaining discharge electrode 12 (generally termed a scanelectrode) and applying a positive voltage (which is positive relativeto the voltage applied to the sustaining discharge electrode 12) to anaddress electrode 21 and to a sustaining discharge electrode 11, wherebya wall charge which helps to initiate a discharge between the sustainingdischarge electrodes 11 and 12 is formed (which is termed writing). Ifan appropriate inverse voltage is applied between the sustainingdischarge electrodes 11 and 12 in this state, a discharge occurs in adischarge space between the two electrodes via a dielectric layer 15(and protection layer 16). After the discharge is completed, if thevoltage applied to the sustaining discharge electrodes 11 and 12 isinverted, a discharge newly occurs. By repeating the foregoingprocedure, a continuous discharge occurs (which is termed a sustaineddischarge or a display discharge).

[0037] In the PDP according to the present embodiment, the addresselectrodes 21 composed of silver or the like and a dielectric layer 22composed of a glass-based material are formed on a rear glass electrode20 and then a barrier rib material similarly composed of a glass-basedmaterial is thin-film printed thereon so that barrier ribs 23 are formedby blast removal using a blast mask. Subsequently, red, green, and bluephosphor layers (24, 25, and 26) are formed successively in stripes onthe barrier ribs 23 in such a manner as to cover the groove surfacesbetween the corresponding barrier ribs 23.

[0038] The phosphor layers (24, 25, and 26) correspond to red, green,and blue colors. The phosphor layers are formed by preparing 40 weightratio of red phosphor particles (60 weight ratio of vehicle), 35 weightratio of green phosphor particles (65 weight ratio of vehicle), and 30weight ratio of blue phosphor particles (70 weight ratio of vehicle),individually mixing the phosphor particles with the vehicles to providephosphor pastes, coating the phosphor pastes by screen printing,evaporating a volatile component from each of the phosphor pastes andburn-removing an organic material therefrom in a paste dry and bakingprocess. The phosphor layers used in the present embodiment are composedof phosphor particles having a median diameter of 3 μm.

[0039] The individual materials of the phosphors are as follows: thematerial of the red phosphor is a 1:1 mixture of the (Y, Gd)BO₃:Euphosphor and the Y₂O₃:Eu phosphor; the material of the green phosphormaterial is the Zn₂SiO₄:Mn phosphor having a Mn/Zn composition ratioadjusted to 0.07 to achieve a {fraction (1/10)} decay time of 6 ms; andthe material of the blue phosphor is a BaMgAl₁₀O₁₄:Eu phosphor.

[0040] Next, the front glass substrate 10 formed with the sustainingdischarge electrodes (11, 12), the bus electrodes (13, 14), thedielectric layer 15, and the protection layer 16 and the rear glasssubstrate 20 are frit-sealed. After the panel is evacuated, a dischargegas is injected therein and sealed. The PDP according to the presentembodiment has a 42″ wide-screen size and the number of pixels (VGA)(852×480) The pitch of one pixel therein is 490 μm×1080 μm.

[0041] Next, the Mn/Zn composition ratio of the Zn₂SiO₄:Mn phosphor wasvaried from 0.01 to 0.1 and plasma display devices were fabricated inthe present embodiment by using the same red-emission and blue-emissionphosphor materials and filling the green-emission phosphor materialshaving the individual Mn/Zn composition ratios in the green phosphorlayers 25. The moving-image qualities and the decay times of the PDPpanels were examined.

[0042] The respective {fraction (1/10)} decay times of the greenphosphors having the Mn/Zn composition ratios of 0.01, 0.03, 0.05, 0.07,0.09, and 0.1 were 12 ms, 10 ms, 8 ms, 6 ms, 4 ms, and 3 ms. In theZn₂SiO₄:Mn phosphors exhibiting a decay characteristic of 4 ms or lessand having a Mn/Zn composition ratio of 0.09 or more, however,significant reductions in brightness, lifetime, and performance wereobserved.

[0043] The red phosphor used in the present embodiment was a 1:1 mixtureof the (Y, Gd)BO₃:Eu phosphor and the (Y₂O₃):Eu phosphor and the{fraction (1/10)} decay time thereof was found to be about 6 ms. As aresult of subjective evaluation during moving-image display, it wasfound that the combination with the green phosphor, which also had adecay time of 6 ms, gave the best impression and the combinations withthe green phosphors, which had decay times of 8 ms and 4 ms, providedthe second best-image qualities.

COMPARATIVE EXAMPLE 1

[0044] In a comparative example, a plasma display device was fabricatedby using a red phosphor composed only of the (Y,Gd)BO₃:Eu phosphor andusing a green phosphor composed of the Zn₂SiO₄:Mn phosphor having aMn/Zn composition ratio of 0.01. The moving-image qualities of theplasma display devices and the decay times of the PDP panels werecompared between

EMBODIMENT 1 and COMPARATIVE EXAMPLE 1

[0045] The {fraction (1/10)} decay time of the plasma display devicefabricated in COMPARATIVE EXAMPLE 1 during green-color display was about12 ms. The decay time of the red phosphor was also as long as about 9 msso that the moving-image quality showed comparatively distinct-tailing.In particular, the green-color decay characteristic was found to beconspicuous.

[0046] The foregoing comparison has showed that the {fraction (1/10)}decay time of the red phosphor of the PDP can be adjusted by using amixture of the (Y,Gd)BO₃:Eu phosphor and the Y₂O₃:Eu phosphor. It hasalso been found that, if the red phosphor had a decay time of about 6ms, the green phosphor preferably has a decay time of about 8 ms to 4 msand optimally a decay time of 6 ms, which is substantially the same asthe decay time of the red phosphor.

[0047] It has also been provided that, in reducing the decay time of theZn₂SiO₄:Mn phosphor composing the green phosphor, the adjustment of theMn/Zn composition ratio thereof is effective and, for the achievement ofa decay time of 8 ms to 4 ms, the composition ratio is preferably in therange of 0.05 to 0.09.

[0048] Although the present embodiment has described the case where theblue phosphor was composed of the BaMgAl₁₀O₁₄:Eu phosphor, the presentinvention is not limited thereto. The present invention is alsoapplicable to phosphor materials other than those mentioned above and tocombinations of phosphor materials other than those mentioned above. Thepresent invention is equally applicable to various particle diametersand sizes.

[0049] The size of a PDP to which the present invention is applicable isnot particularly limited. The present invention is applicableirrespective of parameters determining the sizes of a PDP includingvarious display sizes (ranging from 20 to 100 inches), resolution, andpixel size.

[0050] Embodiment 2

[0051] Since the PDP of a plasma display device according to the presentembodiment has the same structure as the aforementioned PDP shown inFIG. 9, the detailed description thereof will be omitted. In EMBODIMENT1, the decay characteristic when the Mn/Zn ratio of the Zn₂SiO₄:Mnphosphor was varied was shown. The present embodiment performedsubjective evaluation of decay times and moving-image qualities when thecontent of a Y₂O₃:Eu phosphor was varied to 10%, 30%, 50%, 70% and 90%relative to-the mixing ratio between the Y₂O₃:Eu phosphor and a(Y,Gd)BO₃:Eu phosphor each composing the red phosphor.

[0052] The phosphor layers (24, 25, and 26) correspond to red, green,and blue colors in the same manner as in EMBODIMENT 1. The phosphorlayers were formed by preparing 40 weight ratio of red phosphorparticles (60 weight ratio of vehicle) in all cases, 35 weight ratio ofgreen phosphor particles (65 weight ratio of vehicle), and 30 weightratio of blue phosphor particles (70 weight ratio of vehicle),individually mixing the phosphor particles with the vehicles to providephosphor pastes, coating the phosphor pastes by screen printing,evaporating a volatile component from each of the phosphor pastes andburn-removing an organic material therefrom in a paste dry and bakingprocess. The blue-emission phosphor was a BaMgAl₁₀O₁₄:Eu phosphor.

[0053] The decay times of the red phosphors were 8.5 ms, 7.0 ms, 6.0 ms,4.0 ms, and 3.5 ms at the respective mixing ratios (contents of Y₂O₄:Eu)of 10%, 30%, 50%, 70%, and 90%.

[0054] Image display with excellent moving-image qualities was obtainedin the range of 7.0 to 4.0 ms in the vicinity of 6 ms, which is thedecay time of the green phosphor. This proved that the mixing ratio ofthe red phosphor was preferably in the range of about 30% to 70%.

[0055] It has been shown that the {fraction (1/10)} decay time of thered phosphor of the PDP can be adjusted by using a mixture of the(Y,Gd)BO₃:Eu phosphor and the Y₂O₃:Eu phosphor. It has also been foundthat, if the green phosphor had a decay time of about 6 ms, the redphosphor preferably has a decay time of about 8 ms to 4 ms (7 ms to 4 msas a result of the study in the embodiment), which is substantially thesame as the decay time of the green phosphor.

[0056] It was also found that the mixing ratio between the (Y, Gd)BO₃:Euphosphor composing the red phosphor and the Y₂O₃:Eu phosphor waspreferably in the range of 30% to 70% in terms of providing a decay timeof 8 ms to 4 ms. Similar studies were made also in the case where the(Y,Gd)BO₃:Eu phosphor was used in combination with a (Y,Gd) (P,V)O₄:Euphosphor to provide a mixture. In this case, it was found that themixing ratio (content of the (Y,Gd) (P,V)O₄:Eu phosphor) for providing adecay time of 8 ms to 4 ms was preferably in the range of 25% to 95%.

[0057] Although the present embodiment has described the case where theblue phosphor was composed of the BaMgAl₁₀O₁₄:Eu, the present inventionis not limited thereto. The present invention is also applicable tophosphor materials other than those mentioned above and to combinationsof phosphor materials other than those mentioned above. The presentinvention is equally applicable to various particle diameters and sizes.

[0058] The size of a PDP to which the present invention is applicable isnot particularly limited. The present invention is applicableirrespective of parameters determining the sizes of a PDP includingvarious display sizes (ranging from 20 to 100 inches), resolution, andpixel size.

[0059] Embodiment 3

[0060]FIG. 3 is a cross-sectional view showing a structure correspondingto one pixel in a PDP according to the present embodiment. In thepresent embodiment, a green phosphor was filled in the green phosphorlayer 25 by successively printing a (Y,Gd)₃(Al,Ga)₅O₁₂:Tb phosphorexhibiting a decay time of 5 ms and a Zn₂SiO₄:Mn phosphor exhibiting adecay of 8 ms in two steps by screen printing, whereby the greenphosphor layer 25 composed of the two phosphors stacked in layers shownin FIG. 3 was formed.

[0061] The phosphor layers (24, 25, and 26) correspond to red, green,and blue colors in the same manner as in EMBODIMENT 1. The phosphorlayers were formed by preparing 40 weight ratio of red phosphorparticles (60 weight ratio of vehicle), the Zn₂SiO₄:Mn phosphor as 14weight ratio of green phosphor particles (86 weight ratio of vehicle),the (Y,Gd)₃(Al,Ga)₅O₁₂:Tb phosphor (where Tb concentration was 10 mol %)as 20 weight ratio of green phosphor particles (80 weight ratio ofvehicle), and 30 weight ratio of blue phosphor particles (70 weightratio of vehicle), individually mixing the phosphor particles with thevehicles to provide phosphor pastes, coating the phosphor pastes byscreen printing, evaporating a volatile component from each of thephosphor pastes and burn-removing an organic material therefrom in apaste dry and baking process. The individual materials of the phosphorswere as follows: the material composing the red phosphor was a mixtureof a (Y,Gd)BO₃:Eu phosphor and a (Y,Gd) (P,V)O₄:Eu phosphor at a mixingratio of 60%; the material composing the blue phosphor was aBaMgAl₁₀O₁₄:Eu phosphor; and the material composing the green phosphorwas the Zn₂SiO₄:Mn phosphor and a Y₃(Al_(x)Ga_(1-x))₅O₁₂:Tb phosphor(where Tb concentration was 10 mol %), which were prepared individually.

[0062] At that time, the {fraction (1/10)} decay time of the redphosphor was about 6 ms and the decay time of emission obtained from astacking type of green phosphor layer was 6 ms so that substantiallyequal decay characteristics were obtained. Accordingly, a displayedimage with an excellent moving-image quality was obtained.

[0063] To vary a volume ratio in the stacking type of green phosphorlayer, a phosphor paste containing 25 to 10 weight ratio of Zn₂SiO₄:Mngreen phosphor particles (75 to 90 weight ratio of vehicle) and aphosphor paste containing 10 to 25 weight ratio of (Y,Gd)₃(Al,Ga)₅O₁₂:Tbgreen phosphor particles (where Tb concentration was 10 mol %) (90 to 75weight ratio of vehicle) were prepared individually and printingformation was performed under the same conditions as described above.

[0064] The combinations were determined such that the weight ratio ofthe phosphor particles becomes 35 in all cases.

[0065] The decay characteristics when the volume ratio in the stackingtype of green phosphor layer was varied were observed and it was foundthat the respective {fraction (1/10)} decay times were 7 ms, 6.5 ms, 6ms, and 5.5 ms when the contents of the (Y,Gd)₃(Al,Ga)₅O₁₂:Tb phosphorwere about 30%, about 40%, about 60%, and about 70%.

[0066] Thus, it has been proved that the decay times can be adjustedeven in the phosphor layer 25 formed by stacking theY₃(Al_(x)Ga_(1-x))₅O₁₂:Tb phosphor (where Tb concentration was 10 mol %)activated with terbium as a rare earth element and the Zn₂SiO₄:Mnphosphor in layers. If the {fraction (1/10)} decay time of the redphosphor of the PDP is adjusted to about 6 ms by using the mixture ofthe (Y,Gd)BO₃:Eu phosphor and the (Y,Gd) (P,V)O₄:Eu phosphor at a mixingratio of 60%, the decay time of the stacking type of green phosphor filmis preferably about 8 ms to 4 ms (7 ms to 4 ms as a result of the studyin the embodiment) and optimally 6 ms, which is substantially the sameas the decay time of the red phosphor.

[0067] Although the present embodiment has described the case where theblue phosphor was composed of the BaMgAl₁₀O₁₄:Eu, the present inventionis not limited thereto. The present invention is also applicable tophosphor materials other than those mentioned above and to combinationsof phosphor materials other than those mentioned above. The presentinvention is equally applicable to various particle diameters and sizes.

[0068] The size of a PDP to which the present invention is applicable isnot particularly limited. The present invention is applicableirrespective of parameters determining the sizes of a PDP includingvarious display sizes (ranging from 15 to 100 inches), resolution, andpixel size.

[0069] Embodiment 4

[0070] Since the PDP of a plasma display device according to the presentembodiment has the same structure as the aforementioned PDP shown inFIG. 9, the detailed description thereof will be omitted.

[0071]FIG. 4 shows is a view showing the spaces between barrier ribswhich correspond to one pixel in the PDP of the plasma display deviceaccording to the present embodiment. The present embodiment uses therear glass substrate 20 having a structure different from that of therear glass substrate 20 used in each of the foregoing embodiments. Byassuming that the size of a green discharge cell (barrier rib space) is100%, the size of a red discharge cell is 80%, and the size of a bluedischarge cell is 120%, the space between the barrier ribs 23 is allowedto vary by 40% at the maximum.

[0072] The present embodiment evaluated decay characteristics when themixing ratio of the Y₂SiO₅:Tb phosphor (content of a Y₂SiO₅:Tb phosphor)exhibiting a decay time of 4 ms to a Zn₂SiO₃:Mn phosphor exhibiting adecay time of 8 ms was varied.

[0073] The phosphor layers (24, 25, and 26) shown in FIG. 4 were formedby filling the green phosphor in the phosphor layer 25 by screenprinting.

[0074] The phosphor layers (24, 25, and 26) correspond to red, green,and blue colors in the same manner as in EMBODIMENT 1. The phosphorlayers were formed by preparing 35 weight ratio of red phosphorparticles (65 weight ratio of vehicle), the Zn₂SiO₄:Mn phosphor and theY₂SiO₅:Tb phosphor as 40 weight ratio of green phosphor particles (62weight ratio of vehicle), and 50 weight ratio of blue phosphor particles(50 weight ratio of vehicle), individually mixing the phosphor particleswith the vehicles to provide phosphor pastes, coating the phosphorpastes by screen printing, evaporating a volatile component from each ofthe phosphor pastes and burn-removing an organic material therefrom in apaste dry and baking process. The individual materials of the phosphorswere as follows: the material composing the red phosphor was a mixtureof the (Y,Gd)BO₃:Eu phosphor and the (Y,Gd) (P,V)O₄:Eu phosphor at amixing ratio of 60% which has a decay time of about 6 ms. The materialcomposing the blue phosphor was a BaMgAl₁₀O₁₄:Eu phosphor. As a materialcomposing the green phosphor, a mixture of the Zn₂SiO4:Mn phosphor andthe Y₂SiO₅:Tb phosphor at a mixing ratio of 1:1 was prepared.

[0075] The decay characteristics when the mixing ratio (the content ofthe Y₂SiO₅:Tb phosphor) was varied to 10%, 30%, 50%, 70%, and 90% weresuch that the respective {fraction (1/10)} decay times thereof were 7.5ms, 6.5 ms, 6 ms, 5 ms, and 4.5 ms.

[0076] Thus, it has been proved that the decay times can be adjustedeven in the phosphor layer 25 formed by mixing the Zn₂SiO₄:Mn phosphorwith the Y₂SiO₅:Tb phosphor (where Tb concentration was 10 mol %)activated with terbium as a rare earth element. If the {fraction (1/10)}decay time of the red phosphor of the PDP is adjusted to about 6 ms byusing the mixture of the (Y,Gd)BO₃:Eu phosphor and the (Y,Gd) (P,V)O₄:Euphosphor at a mixing ratio of 60%, the decay time of the stacking typeof green phosphor film is preferably about 8 ms to 4 ms (7 ms to 4 ms asa result of the study in the embodiment) and optimally 6 ms, which issubstantially the same as the decay time of the red-emission phosphor.

[0077] Thus, a relative brightness was high and a chromaticity pointhaving an excellent value was obtained. The phosphor mixture of theY₂SiO₅:Tb phosphor activated with terbium as a rare earth element andthe Zn₂SiO₄:Mn phosphor has no limit on the mixing ratio therebetweenand the Tb activated concentration.

[0078] Green phosphor mixture films composed of the followinggreen-emission phosphors as oxide phosphors each activated with terbium(Tb) as a rare earth element were evaluated. The green phosphorsexamined were prepared by selecting successively at least one or morematerials from a group of phosphors containing, as main components, thecompositions represented by the compositional formulae YBO₃:Tb,LuBO₃:Tb, GdBO₃:Tb, ScBO₃:Tb, YPO₄:Tb, and LaPO₄:Tb, which wereevaluated for brightness. The mixing ratio was held constant at 50% andthe concentration or terbium (Tb) as a rare earth element added foractivation was held constant at 5 mol %. A short-decay time was observedwhen each of LuBO₃:Tb, GdBO₃:Tb, ScBO₃:Tb, and YPO₄:Tb, which werephosphors each providing green emission, was mixed with the Zn₂SiO₄:Mnphosphor.

[0079] Although the present embodiment has described the case where theblue phosphor was composed of the BaMgAl₁₀O₁₄:Eu, the present inventionis not limited thereto. The present invention is also applicable tophosphor materials other than those mentioned above and to combinationsof phosphor materials other than those mentioned above. The presentinvention is equally applicable to various particle diameters and sizes.

[0080] The size of a PDP to which the present invention is applicable isnot particularly limited. The present invention is applicableirrespective of parameters determining the sizes of a PDP includingvarious display sizes (ranging from 15 to 100 inches), resolution, andpixel size.

[0081] Embodiment 5

[0082] A description will be given herein below to a display systemusing a PDP according to each of the foregoing embodiments.

[0083]FIG. 5 is a block diagram showing a schematic structure of aplasma display panel 100 using the PDP according to each of theforegoing embodiments. As shown in the drawing, the plasma display panel100 is composed of a PDP 110, data driver circuits (121, 122), a scandriver circuit 130, high-voltage pulse generators (141, 142), and acontrol circuit 150 for controlling each of the foregoing circuits.

[0084] The PDP 110 is the PDP described in each of the foregoingembodiments. The PDP 110 is driven by a dual scan method which divides ascreen into upper and lower parts for simultaneous driving. Accordingly,the two data driver circuits (121, 122) are provided on the longer-sideregions of the PDP 110 to simultaneously drive the upper and loweraddress electrodes 21.

[0085] The scan driver circuit 130 is provided in one of theshorter-side regions of the PDP 110. The scan driver circuit 130 drivesa sustaining discharge electrode 22. The high voltage pulse generator141 generates a high voltage pulse applied from the scan driver circuit130 to the sustaining discharge electrode 22.

[0086] The high voltage pulse generator 142 is provided on the other ofthe shorter-side regions of the PDP 110. The high voltage pulsegenerator 142 generates a high voltage pulse to drive the sustainingdischarge electrode 21.

[0087]FIG. 6 is a block diagram showing a schematic structure of anexample of a plasma display module 200 having the plasma display panel100 shown in FIG. 5. As shown in the drawing, the plasma display model200 is constituted by: a signal processing circuit 210 composed of aninput signal processing circuit 211, an image quality processing circuit212, a frame memory 213, and a scan/data driver control circuit 214; anelectric power supply controller 220; a high voltage power supply 230;and a plasma display panel 100. An input image signal inputted to theplasma display module 200 is subjected to signal processing such as γcorrection in the input signal processing circuit 211 and the imagequality processing circuit 212 and then stored in the frame memory 213.In this case, if the input image signal is an analog signal, it isconverted to digital data in the input signal processing circuit 211.

[0088] The scan/data driver control circuit 214 controls/drives the datadriver circuit (121, 122) and the scan driver circuit 130.

[0089]FIG. 7 is a block diagram showing a schematic structure of anexample of a plasma display monitor 300 having the plasma display module200 shown in FIG. 6. FIG. 8 is a block diagram showing a schematicstructure of an example of a PDP television system 400 having the plasmadisplay module 200 shown in FIG. 6. In FIGS. 7 and 8, 310 is a speakerand 410 is a TV tuner. To the plasma display television monitor 300shown in FIG. 7 and to the plasma display television system 400 shown inFIG. 8, an image, a voice, and a power are supplied from an externalsignal source (such as a personal computer, a video deck, a CD/DVDplayer, an internet terminal, a telephone line, or a digital signalsource) Images obtained from these display systems were high inbrightness and quality. In particular, a tailing phenomenon was reducedduring moving-image display, which proved a high moving-image quality.

[0090] Embodiment 6

[0091] Representative phosphors according to the embodiments of thepresent invention are synthesized as follows. As raw materials for thephosphors, there are used an alkali earth carbonate compound such asstrontium carbonate, a zinc compound such as zinc carbonate, an europiumcompound such as europium fluoride, a silicon compound such as silicondioxide, and a halogenated ammonium compound such as ammonium chloride.These raw materials are weigh-collected in accordance with thecompositional formula and mixed sufficiently in a wet or dry process.Each of the resulting mixtures is filled in a heat-resistant vessel suchas a molten alumina crucible and baked twice. The first baking processis performed in air at 800° C. and the second baking process isperformed in a nitrogen gas atmosphere containing 5% hydrogen at atemperature of 1250° C. The baked materials were ground, washed withwater, and dried to provide the blue-emission phosphors according to thepresent invention.

[0092] Table 1 shows the compositions of the phosphors and the relativeintensities of emission therefrom. TABLE 1 Relative Emission Intensity(%, Excitation Sample No. Composition of Phosphor at 147 nm) 1Ca1.9Eu0.1SiO₄ 110% 2 Sr1.9Eu0.1SiO₄ 110% 3 Ba1.9Eu0.1SiO₄ 100% 4Ba1.9Eu0.1MgSiO₄ 105% 5 (Ba,Sr,Ca)0.9Eu0.1MgSiO₄ 110% 6(Ba,Sr,Ca)0.9Eu0.1(Mg0.9,Zn0.1)SiO₄ 115% 7 (Ca)0.9Eu0.1MgSi₂O₆ 100% 8(Ba,Sr,Ca)0.9Eu0.1(Mg0.9,Zn0.1)Si₂O₆ 110% ComparativeBa0.9MgAl₁₀O₁₇:Eu0.1 100% Sample

[0093] Of the phosphors, the sample 5 was synthesized as follows. Thefollowing raw materials BaCO₃: 0.3 mol×0.1 5.92 g, SrCO₃: 0.3 mol×0.14.42 g, CaCO₃: 0.3 mol×0.1 3.00 g, MgCO₃: 1 mol×0.1 8.43 g, SiO₂: 1mol×0.1 6.01 g, Eu₂O₃: 0.1 mol×0.05 1.76 g, and NH₄Cl: 0.1 g wereweight-collected and mixed sufficiently in required quantities. Theresulting mixture was filled in the heat-resistance vessel such as amolten alumina crucible, baked in air at 800° C., and then baked in anitrogen gas atmosphere containing 5% hydrogen at a temperature of 1250°C. The baked material was ground, washed with water, and dried toprovide the blue-emission phosphor. The other phosphors were similarlysynthesized. Thereafter, the respective relative intensities of emissionfrom the samples were determined by assuming that the brightness ofemission from the currently used BAM phosphor under excitation caused bya vacuum UV beam at 147 nm was 100%. The results were 100% to 115%, asshown in Table 1. It was also proved that the lifetime properties of thephosphors were improved compared with those of comparative samples.

[0094] Embodiment 7

[0095] Phosphors (samples 9 to 20) partly substituted by Ca, Sr, Ba, Mg,or Zn shown in Table 2 were synthesized by using the raw materialslisted above and following a similar synthesizing process. It was foundthat emission from each of the phosphors had a relatively highbrightness under 147 nm UV beam excitation. Specific emissionintensities are shown in Table 2. The lifetime properties of thephosphors were found to be improved compared with those of comparativesamples.

[0096] Embodiment 8

[0097] Plasma display panels (PDPs) were fabricated by using, as bluephosphors each composing a blue phosphor film, divalent europiumactivated alkali earth silicate phosphors (having the compositions shownin Tables 1 and 2) according to the present invention. TABLE 2 RelativeEmission Intensity (%, Excitation Sample No. Composition of Phosphor at147 nm)  9 (Ba,Sr,Ca)0.99Eu0.01MgSiO₄ 105% 10 (Ba,Sr,Ca)0.95Eu0.05MgSiO₄108% 11 (Ba,Sr,Ca)0.8Eu0.2MgSiO₄ 105% 12 (Ba,Sr,Ca)0.7Eu0.3MgSiO₄ 100%13 Ba0.9Eu0.1(Mg0.9,Zn0.1)SiO₄ 110% 14 Ba0.9Eu0.1(Mg0.8,Zn0.2)SiO₄ 110%15 Ba0.9Eu0.1(Mg0.5,Zn0.5)SiO₄ 100% 16 Ba0.9Eu0.1ZnSiO₄  90% 17Ca(Mg0.99,Zn0.01)Si₂O₆ 115% 18 Ca(Mg0.9,Zn0.1)Si₂O₆ 110% 19Ca(Mg0.8,Zn0.2)Si₂O₆ 100% 20 CaZnSi₂O₆  80% Comparative Ba0.9MgAl₁₀O₁₇:Eu0.1 100% Sample

[0098] In PDPs such as the surface-discharge color PDPs according to thepresent embodiment, a discharge is induced by, e.g., applying a negativevoltage to a sustaining discharge electrode (generally termed a scanelectrode) and applying a positive voltage (which is positive relativeto the voltage applied to the sustaining discharge electrode) to anaddress electrode and to a sustaining discharge electrode, whereby awall charge which helps to initiate a discharge between the sustainingdischarge electrodes is formed (which is termed writing) If anappropriate inverse voltage is applied between the sustaining dischargeelectrodes in this state, a discharge occurs in a discharge spacebetween the two electrodes via a dielectric layer (and protectionlayer). After the discharge is completed, if the voltage applied to thesustaining discharge electrodes is inverted, a discharge newly occurs.By repeating the foregoing procedure, a continuous discharge occurs(which is termed a sustained discharge or a display discharge).

[0099] In the PDP according to the present embodiment, the addresselectrodes composed of silver or the like and a dielectric layercomposed of a glass-based material are formed on a rear glass electrodeand then a barrier rib material similarly composed of a glass-basedmaterial is thin-film printed thereon so that barrier ribs are formed byblast removal using a blast mask. Subsequently, red, green, and bluephosphor layers are formed successively in stripes on the barrier ribsin such a manner as to cover the groove surfaces between thecorresponding barrier ribs. The phosphor layers correspond to red,green, and blue colors. The phosphor layers are formed by preparing 40weight ratio of red phosphor particles (60 weight ratio of vehicle), 35weight ratio of green phosphor particles (65 weight ratio of vehicle),and 35 weight ratio of blue phosphor particles (65 weight ratio ofvehicle), individually mixing the phosphor particles with the vehiclesto provide phosphor pastes, coating the phosphor pastes by screenprinting, evaporating a volatile component from each of the phosphorpastes and burn-removing an organic material therefrom in a paste dryand baking process. The phosphor layers used in the present embodimentare composed of phosphor particles each having a center diameter of 3μm. The individual materials of the phosphors are as follows: thematerial of the red phosphor is a 1:1 mixture of a (Y,Gd)BO₃:Eu phosphorand a Y₂O₃:Eu phosphor; and the material of the green phosphor is aZn₂SiO₄:Mn phosphor. Next, the front glass substrate formed with thesustaining discharge electrodes, the bus electrodes, the dielectriclayer, and the protection layer and the rear glass substrate arefrit-sealed. After the panel is evacuated, a discharge gas is injectedtherein and sealed. Each of the PDPs according to the present embodimenthas a 3 screen size and the pitch of one pixel therein is 1000 μm×1000μm.

[0100] Next, plasma display devices were fabricated by using thephosphors formed in EMBODIMENTS 6 and 7, which were filled in therespective phosphor layers 25. As the red and green phosphors, the samematerials were used. The initial brightnesses and lifetime properties ofthe plasma display devices were examined. The panel obtained had a moreexcellent color tone, a higher brightness, and a longer lifetime than aconventional panel fabricated by replacing only the blue phosphor with adivalent europium activated barium magnesium aluminate. As a result ofexamination, the initial brightnesses were nearly equal to the relativeintensities of emission from the powders shown in relation to theindividual phosphors in Table 2 and the lifetime performance of each ofthe phosphors (each of the compositions shown in Tables 1 and 2) waslonger than that of each of the comparative phosphors.

[0101] Although the present embodiment has not shown a detailed resultof examination performed with respect to the red and green phosphors, aPDP can also be fabricated in the same manner if each of phosphorshaving the following compositions is used. The red phosphor may includeone or more of (Y,Gd)BO₃:Eu, (Y,Gd)₂O₃:Eu, and (Y,Gd) (P,V)O₄:Euphosphors. The green phosphor may include one or more selected from thegroup consisting of Zn₂SiO₄:Mn, (Y,Gd,Sc)₂SiO₅:Tb,(Y,Gd)₃(Al,Ga)₅O₁₂:Tb, (Y,Gd)₃ (Al,Ga)₅O₁₂:Ce, (Y,Gd)B₃O₆:Tb, and(Y,Gd)PO₄: Tb. A combination with a phosphor not shown herein can alsobe used.

[0102] Embodiment 9

[0103]FIG. 10 shows the dependence of the relative color-difference ofSr_(3-x)MgSi₂O₈:Eu_(x) on Eu concentration when the color-differencebetween the uniform-chromaticity coordinates (U, V) of fluorescentcolors and an NTSC-based blue color point is assumed to be 100%. Fromthe drawing, excellent color tones are obvious since the colors obtainedin the present embodiment are closer to the NTSC blue color point thanthe color obtained from the currently used BAM phosphor in the range inwhich the Eu concentration (x) satisfies 0.01≦x≦0. The luminousefficiencies were at the same level as that of the BAM phosphor and thelifetime was also long. Table 3 shows the compositions of the phosphorsand the relative color-differences of emission therefrom. TABLE 3Relative Color-Difference of Composition of Emission (%, ExcitationSample No. Phosphor at 147 nm) 21 Sr2.99Eu0.01MgSi₂O₈ 99% 22Sr2.98Eu0.02MgSi₂O₈ 86% 23 Sr2.97Eu0.03MgSi₂O₈ 82% 24Sr2.95Eu0.05MgSi₂O₈ 80% 25 Sr2.90Eu0.10MgSi₂O₈ 98% Comparative Ba0.9MgAl₁₀O₁₇:Eu0.1 100%  Sample

[0104] The sample 24 was synthesized as follows. The following rawmaterials SrCO₃: 4.385 g, MgCO₃: 0.907 g, SiO₂: 1.00 g, Eu₂O₃: 0.053 g,NH₄Cl: 00.22 g were mixed sufficiently. The resulting mixture was filledin the heat-resistance vessel such as a molten alumina crucible, bakedin air at 800° C., and then baked in a nitrogen gas atmospherecontaining 5% hydrogen at a temperature of 1250° C. The baked materialwas ground, washed with water, and dried to provide a blue-emissionphosphor. The relative color-difference of the sample 4 when thecolor-difference between the isochromatic coordinates (U, V) offluorescent colors and the NTSC-based blue color point is assumed to be100% is 80%. This indicates an excellent color tone since the colorobtained in the present embodiment is closer to the NTSC blue colorpoint than that of the currently used BAM phosphor. Likewise, thesamples 21, 22, 23, and 25 were synthesized. The phosphors exhibitedexcellent relative color-differences of 99, 86, 82, and 87%.

[0105] The foregoing results are shown in FIG. 10 as the dependence ofthe relative color-difference of the phosphor in question on Euconcentration (x). From the drawing, it is obvious that the effectiverange of Eu is 0.01≦x≦0.1. It is to be noted that the brightness ofemission from the phosphor falling within the Eu concentration range isat the same level as emission from the BAM phosphor.

[0106] Embodiment 10

[0107] Phosphors (samples 26 to 40) partly substituted by Ca, Sr, Ba,Mg, or Zn shown in Table 3 were synthesized by using the raw materialslisted above and following a similar synthesizing process. It was foundthat emission from each of the phosphors had a relatively highbrightness under 147 nm UV beam excitation.

[0108] Embodiment 11

[0109] Plasma display panels (PDPs) were fabricated by using, as bluephosphors each composing a blue phosphor film, divalent europiumactivated alkali earth silicate phosphors (having the compositions shownin Tables 3 and 4) according to the present invention. TABLE 4 RelativeEmission Intensity (%, Excitation Sample No. Composition of Phosphor at147 nm) 26 Sr2.87Ca0.1Eu0.03MgSi₂O₈ 100% 27Sr2.96Ca0.03Eu0.99Zn0.01Si₂O₈ 100% 28 Sr2.87Ca0.1Eu0.03Mg0.99Zn0.01Si₂O₈103% 29 Ca2.9Eu0.1MgSi₂O₈ 100% 30 Ca2.4Ba0.5Eu0.1MgSi₂O₈ 105% 31Sr2.8Ba0.1Eu0.1MgSi₂O₈ 100% 32 Sr2.4Ba0.5Eu0.1MgSi₂O₈ 110% 33Sr1.9Ba1.0Eu0.1MgSi₂O₈ 115% 34 Sr0.9Ba2.0Eu0.1MgSi₂O₈ 115% 35Ba2.9Eu0.1MgSi₂O₈ 110% 36 Sr2.4Ba0.5Eu0.1Mg0.99Zn0.01Si₂O₈ 115% 37Sr2.3Ba0.5Ca0.1Eu0.1Mg0.99Zn0.01Si₂O₈ 115% 38 Sr2.49Ba0.5Eu0.01MgSi₂O₈100% 39 Sr2.45Ba0.5Eu0.05MgSi₂O₈ 105% 40 Sr2.3Ba0.5Eu0.2MgSi₂O₈ 110%Comparative Ba0.9Mg Al₁₀O₁₇:Eu0.1 100% Sample

[0110] In PDPs such as the surface-discharge color PDPs according to thepresent embodiment, a discharge is induced by, e.g., applying a negativevoltage to a sustaining discharge electrode (generally termed a scanelectrode) and applying a positive voltage (which is relative to thevoltage applied to the sustaining discharge electrode) to an addresselectrode and to a sustaining discharge electrode, whereby a wall chargewhich helps to initiate a discharge between the sustaining dischargeelectrodes is formed (which is termed writing). If an appropriateinverse voltage is applied between the sustaining discharge electrodesin this state, a discharge occurs in a discharge space between the twoelectrodes via a dielectric layer (and protection layer). After thedischarge is completed, if the voltages applied to the sustainingdischarge electrodes is inverted, a discharge newly occurs. By repeatingthe foregoing procedure, a continuous discharge occurs (which is termeda sustained discharge or a display discharge).

[0111] In the PDP according to the present embodiment, the addresselectrode composed of silver or the like and a dielectric layer composedof a glass-based material are formed on a rear glass electrode and thena barrier rib material similarly composed of a glass-based material isthin-film printed thereon so that barrier ribs are formed by blastremoval using a blast mask. Subsequently, red, green, and blue phosphorlayers are formed successively in stripes on the barrier ribs in such amanner as to cover the groove surfaces between the corresponding barrierribs. The phosphor layers correspond to red, green, and blue colors. Thephosphor layers are formed by preparing 40 weight ratio of red phosphorparticles (60 weight ratio of vehicle), 35 weight ratio of greenphosphor particles (65 weight ratio of vehicle), and 35 weight ratio ofblue phosphor particles (65 weight ratio of vehicle), individuallymixing the phosphor particles with the vehicles to provide phosphorpastes, coating the phosphor pastes by screen printing, evaporating avolatile component from each of the phosphor pastes and burn-removing anorganic material therefrom in a paste dry and baking process. Thephosphor layers used in the present embodiment are composed of phosphorparticles each having a center diameter of 3 μm. The individualmaterials of the phosphors are as follows: the material of the redphosphor is a 1:1 mixture of a (Y,Gd)BO₃:Eu phosphor and a Y₂O₃:Euphosphor: and the material of the green phosphor is a Zn₂SiO₄:Mnphosphor. Next, the front glass substrate formed with the sustainingdischarge electrodes, the bus electrodes, the dielectric layer, and theprotection layer and the rear glass substrate are frit-sealed. After thepanel is evacuated, a discharge gas is injected therein and sealed. Eachof the PDPs according to the present embodiment has a 3 screen size andthe pitch of one pixel therein is 1000 μm×1000 μm.

[0112] Next, plasma display devices were fabricated by using thephosphors formed in EMBODIMENTS 6 and 7, which were filled in therespective phosphor layers 25. As the red and green phosphors, the samematerials were used. The initial brightnesses and lifetime properties ofthe plasma display devices were examined.

[0113] The panel obtained had an excellent color tone, a higherbrightness, and a longer lifetime than a conventional panel fabricatedby replacing only the blue phosphor with a divalent europium activatedbarium magnesium aluminate phosphor.

[0114] As a result of examination, the relative intensities of emissionshown in relation to the individual phosphors in Table 4 were obtainedand the initial brightnesses were equal or superior to those of emissionfrom the divalent europium activated barium magnesium aluminatephosphors as comparative samples. The result also showed the lifetimeperformance of each of the phosphors (each of the compositions shown inTables 3 and 4) which was superior to that of each of the comparativephosphors.

[0115] Although the present embodiment has not shown a detailed resultof examination performed with respect to the red and green phosphors, aPDP can also be fabricated in the same manner if each of phosphorshaving the following compositions is used. The red phosphor may includeone or more of (Y,Gd)BO₃:Eu, (Y,Gd)₂O₃:Eu, and (Y,Gd) (P,V)O₄:Euphosphors. The green phosphor may include one or more selected from thegroup consisting of (Y,Gd,Sc)₂SiO₅:Tb, (Y,Gd)₃(Al,Ga)₅O₁₂:Tb,(Y,Gd)₃(Al,Ga)₅O₁₂:Ce, (Y,Gd)B₃O₆:Tb, and (Y,Gd)PO₄:Tb phosphors. Acombination with a phosphor not shown herein can also be used.

[0116] Embodiment 12

[0117] Rare-gas (xenon) discharge cool white fluorescent lamps werefabricated by using the divalent europium activated alkali earthsilicate phosphors (having the compositions shown in Tables 1 and 3)according to the present invention as blue phosphors, divalent manganeseactivated zinc silicate phosphors as green phosphors, and trivalenteuropium activated yttrium gadolinium oxide phosphors as red phosphors.Each of the lamps had a higher luminous efficiency and a longer lifetimethan a conventional lamp fabricated by replacing only the blue phosphorwith a divalent europium activated barium magnesium aluminate phosphor.

[0118] Embodiment 13

[0119] Flat-panel rare-gas (xenon) discharge cool white fluorescentlamps were fabricated by using the divalent europium activated alkaliearth silicate phosphors (having the compositions shown in Tables 2 and4) according to the present invention as blue phosphors, divalentmanganese activated zinc silicate phosphors as green phosphors, andtrivalent europium activated yttrium gadolinium oxide phosphors as redphosphors. Each of the lamps had a higher luminous efficiency and alonger lifetime than a conventional lamp fabricated by replacing onlythe blue phosphor with a divalent europium activated barium magnesiumaluminate phosphor.

[0120] Embodiment 14

[0121] Here, uniform transparent electrodes are formed initially on theinner surfaces of glass substrates to be formed with phosphor films.Then, the divalent europium activated alkali earth silicate phosphors(having the compositions shown in Tables 1 to 4) according to thepresent invention, the divalent manganese activated zinc silicatephosphors, and the trivalent europium activated yttrium gadolinium oxidephosphors were formed successively as blue phosphors composing bluephosphor films, as green phosphors composing green phosphor films, andas red phosphors composing red phosphors, respectively. Each of theglass substrates and the other glass substrate into which an extremelysmall electron beam source has been incorporated were bonded to eachother in integral relation, sealed, and evacuated, whereby 10 screenfield-emission display (FED) panels were fabricated. Each of the panelsshowed such characteristics as a higher efficiency and a longer lifetimethan a conventional FED panel fabricated by replacing only the bluephosphor with a divalent europium activated barium magnesium aluminatephosphor. As a result of constructing display panels by using thesepanels and using them as display systems in a television, a video, anautomobile, and the like, it was found that high display qualities wereobtainable. Thus, longer lifetimes and higher image qualities wereachieved by using blue phosphors (divalent europium activated alkaliearth silicate phosphors) each having a high efficiency under excitationcaused by a vacuum UV beam and a low-speed electrode beam in rare-gasdischarge display/luminescent devices or in field-emission display (FED)devices.

[0122] Embodiment 15

[0123] As raw materials, BaCO₃ (2.98 xmol %) [0≦x≦1], SrCO₃ (2.98(1-x)mol %), MgCO₃ (1 mol %), SiO₂ (2 mol %) and Eu₂O₃ (0.01 mol %) wereweigh-collected and mixed. The resulting mixture was baked in an aluminacrucible at 1300° C. for three hours. The baked material was ground andbaked in a reducing atmosphere at 1300° C. for three hours. The bakedmaterial was ground by using a ball mill, washed with water, classified,and dried to provide a phosphor represented by(Ba_(x)Sr_(1-x)2.98)MgSi₂O₈:Eu_(0.02) [0≦x≦1]. A phosphor paste wasprepared by mixing 40 weight ratio of the present phosphor with 60weight ratio of a vehicle, coated by screen printing on a glasssubstrate, and dried. A phosphor film was formed by performing a bakingprocess and thereby removing a volatile component and an organicmaterial from the paste.

[0124] A baked paste powder was produced by peeling off the phosphorfrom the upper surface of the glass substrate and the intensity (A1) ofemission from the baked paste powder under excitation caused by anexcimer lamp (at a center wavelength of 146 nm) was measured. At thesame time, the intensity (A0) of emission from the original phosphorpowder, which was unprinted and unbaked, was also measured. As an indexindicative of degradation in the paste baking process, a maintenancefactor of emission in intensity (A=A1/A0×100) was used. For comparison,similar measurement was performed also for a BAM phosphor used commonlyas a blue phosphor. FIG. 11 shows the maintenance factor of emission inintensity/brightness (A). It was proved that, when the paste was baked,the (Ba_(x)Sr_(1-x)3-a)MgSi₂O₈:Eu_(a) [0≦x≦0.1 or 0.65≦x≦1] had a highermaintenance factor of emission in intensity and more excellentcharacteristics with reduced degradation than the BAM phosphor.

[0125] Embodiment 16

[0126] By using a phosphor according to the present invention, a PDP wasfabricated and a driving degradation characteristic thereof wasmeasured. FIG. 9 is a schematic view of a display panel in the PDP. ThePDP was obtained by bonding a front glass substrate and a rear glasssubstrate to each other in integral relation. After the formation ofaddress electrodes and barrier ribs on the rear glass substrate,Ba₃MgSi₂O₈:Eu phosphor layers were formed between the barrier ribs. Aphosphor paste was prepared by mixing 40 weight ratio of the phosphorwith 60 weight ratio of a vehicle and coated by screen printing. Avolatile component in the paste was removed and an organic material wasburn-removed therefrom in a paste dry and baking process, whereby thephosphor layers were formed on the rear glass substrate. The rear glasssubstrate formed with the phosphor layers and the front glass substratewere bonded to each other to fabricate a plasma display panel in which adischarge gas has been sealed. The driving-time-varying characteristicof the emission intensity of the plasma display panel was measured bymeasuring an emission intensity (B0) at the initiation of panel drivingand an emission intensity (B1) when 500 hours elapsed after paneldriving. As an index indicative of degradation caused by panel driving,a maintenance factor of emission in intensity (B=B1/B0×100) was used.The result of measurement is shown in FIG. 12. For comparison, similarmeasurement was performed for a BAM phosphor used commonly as a bluephosphor.

[0127] It was proved that the (Ba_(x)Sr_(1-x)3-a)MgSi₂O₈:Eu_(a) phosphor[0≦x≦0.1. or 0.65≦x≦1] had a higher maintenance factor of emission inintensity when the panel was driven and more excellent characteristicswith reduced degradation than the BAM phosphor.

[0128] Although the invention achieved by the present inventors has beendescribed specifically based on the embodiments thereof described above,the present invention is not limited to the foregoing embodiments. It isto be understood that various changes and modifications may be made inthe present invention without departing from the spirit and scopethereof.

[0129] The present invention reduces decay times in a plasma displaydevice and a luminescent device, improves the moving-image qualitythereof, and implements an image display system having a longer lifetimeand a high image quality.

What is claimed is:
 1. A plasma display device comprising: a plasmadisplay panel having at least a pair of substrates disposed in spacedapart and opposing relation, a discharge gas space formed between thepair of substrates to contain a gas sealed therein which generates a UVbeam when it is discharged, electrodes formed on respective opposingsurfaces of the pair of substrates, and a phosphor layer formed on thesurface of one of the pair of substrates in contact with the dischargegas space; and a driving circuit for driving the plasma display panelvia the electrodes, a decay time ({fraction (1/10)} decay time) of lightgenerated from each of phosphor layers for providing red, green, blueemission which compose the phosphor layer being not more than 8 ms. 2.The plasma display device of claim 1, wherein the green phosphor layeris composed of a Zn₂SiO₄:Mn phosphor having a Mn/Zn composition ratio of0.04 or more.
 3. The plasma display device of claim 2, wherein the Mn/Zncomposition of the Zn₂SiO₄:Mn phosphor which is a material composing thegreen phosphor layer is not less than 0.06 and not more than 0.10. 4.The plasma display device of claim 1, wherein the green phosphor layerhas a composition such that a Zn₂SiO₄:Mn phosphor is mixed with one ormore selected from the group consisting of (Y,Gd,Sc)₂SiO₅:Tb,(Y,Gd)₃(Al,Ga)₅O₁₂:Tb, (Y,Gd)₃(Al,Ga)₅O₁₂:Ce, and (Y,Gd)B₃O₆:Tbphosphors.
 5. The plasma display device of claim 4, wherein theZn₂SiO₄:Mn phosphor which is a material composing the green phosphorlayer has a Mn/Zn composition ratio of 0.04 or more.
 6. A plasma displaydevice comprising: a plasma display panel having at least a pair ofsubstrates disposed in spaced apart and opposing relation, a dischargegas space formed between the pair of substrates to contain a gas sealedtherein which generates a UV beam when it is discharged, electrodesformed on respective opposing surfaces of the pair of substrates, and aphosphor layer formed on the surface of one of the pair of substrates incontact with the discharge gas space; and a driver circuit for drivingthe plasma display panel via the electrodes, a decay time ({fraction(1/10)} decay time) of light generated from each of phosphor layers forproviding red, green, blue emission which compose the phosphor layerbeing not more than 6 ms and a decay time difference between emissiongenerated from the red phosphor layer and emission generated from thegreen phosphor layer is not more than 2 ms.
 7. The plasma display deviceof claim 6, wherein the green phosphor layer is composed of a Zn₂SiO₄:Mnphosphor having a Mn/Zn composition ratio of 0.04 or more.
 8. The plasmadisplay device of claim 7, wherein the Mn/Zn composition of theZn₂SiO₄:Mn phosphor which is a material composing the green phosphorlayer is not less than 0.06 and not more than 0.10.
 9. The plasmadisplay device of claim 6, wherein the green phosphor layer has acomposition such that a Zn₂SiO₄:Mn phosphor is mixed with one or morephosphors selected from the group consisting of (Y,Gd,Sc)₂SiO₅:Tb,(Y,Gd)₃(Al,Ga)₅O₁₂:Tb, (Y,Gd)₃(Al,Ga)₅O₁₂:Ce, (Y,Gd)B₃O₆:Tb, and YBO₃:Tbphosphors.
 10. The plasma display device of claim 9, wherein theZn₂SiO₄:Mn phosphor which is a material composing the green phosphorlayer has a Mn/Zn composition ratio of 0.04 or more.
 11. The plasmadisplay device of claim 1, wherein the green phosphor layer has acomposition such that a Zn₂SiO₄:Mn phosphor is mixed with one or moreselected from the group consisting of Y₂SiO₅:Tb, (Y,Gd)₃(Al,Ga)₅O₁₂:Tb,(Y,Gd)B₃O₆:Tb, and YBO₃:Tb phosphors and a mixing ratio thereof(proportion of Zn₂SiO₄) ranges from 40% to 80%.
 12. The plasma displaydevice of claim 1, wherein the red phosphor layer is mixed with any oneor more of a (Y,Gd)BO₃:Eu phosphor, Y₂O₃:Eu, and (Y,Gd) (P,V)O₄:Euphosphors.
 13. The plasma display device of claim 12, wherein the mixingratio (proportion of (Y,Gd)BO₃:Eu) ranges from 50% to 90%.
 14. An imagedisplay system comprising: a plasma display device comprising a plasmadisplay panel having at least a pair of substrates disposed in spacedapart and opposing relation, a discharge gas space formed between thepair of substrates to contain a gas sealed therein which generates a UVbeam when it is discharged, electrodes formed on respective opposingsurfaces of the pair of substrates, and a phosphor layer formed on thesurface of one of the pair of substrates in contact with the dischargegas space and a driver circuit for driving the plasma display panel viathe electrodes, a decay time ({fraction (1/10)} decay time) of lightgenerated from each of phosphor layers for providing red, green, blueemission which compose the phosphor layer being not more than 8 ms. 15.A luminescent device comprising a phosphor film containing ablue-emission divalent europium activated alkali earth silicate phosphorrepresented by the following chemical formula:(Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y):Eu_(c) (wherein Ae is at least one alkaliearth element selected from Sr, Ca, and Ba; Ae′ is at least one elementselected from Mg and Zn; a is 1, 2, or 3; b is 1 or 0; x is 1 or 2; andy is 4, 6, 7, or 8).
 16. The luminescent device of claim 15, wherein theblue-emission divalent europium activated alkali earth silicate phosphoris represented by the following compositional formula:(Ae)_(2-c)(Ae′)Si₂O₇:Eu_(c) (wherein Ae is at least one alkali earthelement selected from Sr, Ca, and Ba; Ae′ is at least one elementselected from Mg and Zn; and c satisfies 0.01≦x≦0.3).
 17. Theluminescent device of claim 15, wherein the blue-emission divalenteuropium activated alkali earth silicate phosphor is represented by thefollowing compositional formula: (Ae)_(1-c)(Ae′)Si₂O₆:Eu_(c) (wherein Aeis at least one alkali earth element selected from Sr, Ca, and Ba; Ae′is at least one element selected from Mg and Zn; and c satisfies0.0≦x≦0.3).
 18. The luminescent device of claim 15, wherein theblue-emission divalent europium activated alkali earth silicate phosphoris represented by the following compositional formula: (Ae)₃(Ae′)Si₂O₈:Eu_(c) (wherein Ae is at least one alkali earth elementselected from Sr, Ca, and Ba; and Ae′ is at least one alkali earthelement selected from Mg and Zn).
 19. The luminescent device of claim18, wherein the blue-emission divalent europium activated alkali earthsilicate phosphor is represented by the following compositional formula:((Sr_(1-y), Ba_(y))_(3-x)(Ae′)Si₂O₈:Eu_(x) (wherein y satisfies 0≦y≦1).20. The luminescent device of claim 18, wherein the blue-emissiondivalent europium activated alkali earth silicate phosphor isrepresented by the following compositional formula: ((Sr_(1-y),Ba_(y))_(3-x)(Ae′)Si₂O₈:Eu_(x) (wherein y satisfies 0≦y≦0.1 or0.65≦y≦0.1).
 21. The luminescent device of claim 19 or 20, wherein x isin the range of 0.01≦x≦0.l in the compositional formula of theblue-emission divalent europium activated alkali earth silicatephosphor.
 22. The luminescent device of any one of claims 15 to 21,wherein the Ae′ site in the compositional formula of the blue-emissiondivalent europium activated alkali earth silicate phosphor isrepresented by (Mg_(1-d)Zn_(d)) and d is in the range of 0<d≦1.
 23. Theplasma display device of any one of claims 1 to 13, wherein theblue-emission phosphor has, as a part thereof, the blue-emissiondivalent europium activated alkali earth silicate phosphor recited inany one of claims 15 to
 22. 24. A luminescent device comprising aphosphor film containing a blue-emission divalent europium activatedalkali earth silicate phosphor represented by the following chemicalformula: (Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y): Eu_(c) (wherein Ae is at leastone alkali earth element selected from Sr, Ca, and Ba; Ae′ is at leastone element selected from Mg and Zn; a is 1, 2, or 3; b is 1 or 0; x is1 or 2; and y is 4, 6, 7, or 8).
 25. An image display system using aflat-panel rare-gas discharge fluorescent lamp comprising a phosphorfilm containing a blue-emission divalent europium activated alkali earthsilicate phosphor represented by the following chemical formula:(Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y):Eu_(c) (wherein Ae is at least one alkaliearth element selected from Sr, Ca, and Ba; Ae′ is at least one elementselected from Mg and Zn; a is 1, 2, or 3; b is 1 or 0; x is 1 or 2; andy is 4, 6, 7, or 8).
 26. An image display system using athree-wavelength cool white fluorescent lamp comprising a phosphor filmcontaining a blue-emission divalent europium activated alkali earthsilicate phosphor represented by the following chemical formula:(Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y):Eu_(c) (wherein Ae is at least one alkaliearth element selected from Sr, Ca, and Ba; Ae′ is at least one elementselected from Mg and Zn; a is 1, 2, or 3; b is 1 or 0; x is 1 or 2; andy is 4, 6, 7, or 8).
 27. An image display system using a field-emissiondisplay device comprising a phosphor film containing a blue-emissiondivalent europium activated alkali earth silicate phosphor representedby the following chemical formula: (Ae)_(a-c)(Ae′)_(b)Si_(x)O_(y):Eu_(c)(wherein Ae is at least one alkali earth element selected from Sr, Ca,and Ba; Ae′ is at least one element selected from Mg and Zn; a is 1, 2,or 3; b is 1 or 0; x is 1 or 2; and y is 4, 6, 7, or 8).